This invention relates to a molded laminate comprising a thermoplastic resin layer of a polyamide resin, an ethylene-vinyl alcohol copolymer, etc. and an adhesive polymer composition layer exhibiting excellent heat fusion-bond properties, particularly excellent heat fusion-bond properties in a high-temperature atmosphere, to the thermoplastic resin layer.
Polyamide resins and ethylene-vinyl alcohol copolymers have been widely used in industrial equipment, domestic appliances, and the like for their excellence in toughness, heat resistance, wear resistance, and gas barrier properties. Applications taking advantage of their gas barrier properties include gas containers and gas pipes. An elastic body, such as a gasket or a sealing part, is inserted into or laminated at a joint of these molded products to secure air tightness or to facilitate handling. The advantage of the gas barrier properties is also exploited in developing packaging materials for foods calling for sealing. In particular, they find wide use in the field of drink bottles and food packaging, etc. It has been studied to laminate a polyester resin layer excellent in heat resistance, chemical resistance and mechanical characteristics, e.g., polyethylene terephthalate, with a polyamide resin layer to improve the gas barrier properties of the polyester resin, and to apply the laminate to containers for carbonated beverages, etc. and long-life packages which extend the shelf life of perishable foods, etc.
Apart from the above-described purposes, an elastic material can be laminated on a molded article for the purpose of imparting flexibility or waterproofness or improving impact resistance or feel to the touch. Vulcanized rubber has frequently been used as such an elastic material. However, because vulcanized rubber has poor heat fusion-bond properties to a polyamide resin or an ethylene-vinyl alcohol copolymer, when these materials are laminated, the interlaminar adhesion is insufficient, and bonding these materials requires an additional step, such as a step of applying a primer, e.g., an adhesive, to the joint area or a step of roughening the joint area.
In laminating a polyester resin layer with a polyamide resin layer, which are not welded together, it has been proposed that a composite material with an adhesive or an adhesive resin is produced. There is a problem, however, that the adhesive strength can reduce in high temperature treatment, such as sterilization or retorting in the food industry, easily resulting in delamination.
On the other hand, a polyester type thermoplastic elastomer comprising a copolymer containing a polyalkylene ether glycol segment is attracting attention as a substitute for vulcanized rubber because of its flexibility. However, it has poor heat fusion-bond properties to a polyamide resin or an ethylene-vinyl alcohol copolymer, providing weak adhesion particularly in a high temperature atmosphere, also causing delamination.
The present invention has been completed in the light of the above-mentioned circumstances. An object of the present invention is to provide a molded laminate comprising a thermoplastic resin layer of a polyamide resin, an ethylene-vinyl alcohol copolymer, etc. and an adhesive polymer composition layer having excellent heat fusion-bond properties to the resin layer, particularly excellent heat fusion-bond properties in a high-temperature atmosphere.
As a result of intensive investigations for settling the above problems, the present inventors have found that an adhesive polymer composition comprising a modified polyester type elastomer obtained by modifying a saturated polyester type thermoplastic elastomer containing a specific amount of a polyalkylene ether glycol segment with an unsaturated carboxylic acid or a derivative thereof in the presence of a radical generator is excellent in heat fusion-bond properties, particularly heat-resistant adhesion, to a thermoplastic resin, such as a polyamide resin and an ethylene-vinyl alcohol copolymer. The present invention has been reached based on this finding.
The gist of the present invention consists in a molded laminate with excellent adhesive strength which comprises an adhesive polymer composition layer and a gas-barrier resin layer comprising a polyamide resin or an ethylene-vinyl alcohol copolymer, the adhesive polymer composition layer comprising a modified polyester type elastomer obtained by modifying a saturated polyester type thermoplastic elastomer having a polyalkylene ether glycol segment content of 58 to 73% by weight with an unsaturated carboxylic acid or a derivative thereof in the presence of a radical generator.
Another gist of the invention resides in the molded laminate characterized in that the adhesive polymer composition has an MFR (measured at 230xc2x0 C. under 2.16 kg load according to JIS K7210) of 40 to 300 (g/10 min).
Still another gist of the invention lies in that a molded laminate characterized in that a base resin layer comprising at least one of a polyester type resin, a styrene type resin, a polycarbonate type resin, an acrylic type resin, and a urethane type resin is laminated with the gas barrier resin layer via the adhesive polymer composition layer.
Yet another gist of the invention exists in that the molded laminate characterized in that the modified polyester type elastomer has an amount of modification of 0.01 to 15 as obtained by an infrared absorption spectrum method, the amount of modification being represented by:
A1786/(Astxc3x97r)
[wherein A1786 is a peak intensity at 1786 cmxe2x88x921 of a 20 xcexcm thick film of a modified polyester type elastomer; Ast is a peak intensity at a reference wavenumber of a 20 xcexcm thick film of a standard sample (a saturated polyester type elastomer having a polyalkyl ether glycol segment content of 65% by weight); and r is the quotient of the mole fraction of the polyester segment in the modified polyester type elastomer divided by the mole fraction of the polyester segment in the standard sample].
An additional gist of the invention consists in the molded laminate characterized in that the compounding ratio of the radical generator is 0.001 to 3 parts by weight per 100 parts by weight of the saturated polyester type thermoplastic elastomer.